1. Field of the Invention
The present invention relates to a plasma display panel (PDP), a kind of light emitting device which displays image information by the use of a gas discharge, and more particularly to a plasma display panel (PDP) that has improved discharge sustaining electrodes pairing up and mutually discharging to maintain light emission of cells for a given period of time, thereby enhancing the discharge efficiency and luminance.
2. Discussion of Related Art
A color PDP is a light emitting device that displays image information by using a gas discharge produced therein, and there is no need to provide an active device to each cell, thus simplifying the manufacturing process, easily increasing the size of a screen, and assuring a high response speed. Therefore, it is used for a display device with a large screen, particularly, a wall-mounted television, a high definition television, indoor/outdoor ad display devices.
In addition, since the PDP can be easily manufactured in larger size than a conventional liquid crystal display, it is suitable for large-sized display devices of more than 40 inches. According to its schematic structure, two glass substrates are coupled to each other by a frit glass, and a very small space between the two glasses is sealed. The sealed space is filled with a gas at 100 to 600 Torr, and a penning gas containing He and Xe is commonly used.
In the display each intersection of plural electrodes defines a single cell. A voltage of more than 100V is applied to intersecting electrodes at the time of driving, and the single cell can be energized to produce a gas discharge forming one element of dot-matrix display.
The PDP is characterized as two-electrode, three-electrode, four-electrode types according to the number of electrodes assigned to each cell. The two-electrode PDP has two electrodes, and voltages for addressing and for sustaining are applied together. The three-electrode PDP is called xe2x80x98sheet discharge PDPxe2x80x99, and is switched or maintained by the voltage applied to electrodes positioned on the side of the discharging cell.
Referring to FIGS. 1 to 3, a device will be described by way of an example.
FIG. 1 depicts upper and lower substrates of a PDP, and an upper substrate 1 of a display panel and a lower substrate 2 are coupled to each other in parallel with a given interval. A common electrode C and a scan electrode S are paired as discharge sustaining electrodes for maintaining light emission of cells in one pixel on upper substrate 1, and a dielectric layer 5 that limits discharge current of the two electrodes and provides insulation between the electrode pair is formed on upper substrate 1. A protective layer 6 is formed on dielectric layer 5. Lower substrate 2 includes barrier ribs 3 forming plural discharging spaces, i.e. cells; a plurality of address electrodes A formed in parallel with barrier ribs 3 and carrying out address discharge at each intersection of scan electrode S and them to produce vacuum ultraviolet rays; fluorescent layers 4 formed on both barrier ribs 3 and lower substrate 2, thus emitting a visible ray during address discharging.
The discharge sustaining electrodes that are paired each have a width of 300 xcexcm, as shown in FIG. 2, and include ITO electrodes 7 and BUS electrodes 8. ITO electrode 7 is formed of a transparent material, and once voltage is applied to both ends, mutual sheet discharge occurs within the corresponding discharging cell. BUS electrodes 8, formed of a metal, each have a width of 50 to 100 xcexcm, and are respectively deposited on ITO electrodes 7 to prevent voltage drop due to the resistance of ITO electrodes.
FIG. 2 is a sectional view of a cell while the upper and lower substrates are coupled to each other, and FIGS. 3a and 3b depict conventional discharge sustaining electrodes.
The process of displaying the image information according to the conventional PDP is as follows. When a voltage for starting discharge is applied between scan electrode S and common electrode C, sheet discharge occurs between two electrodes to produce wall electric charge within the corresponding discharging cell. After that, as an address discharge voltage is applied to scan electrode S and corresponding address electrode A, a writing discharge occurs within the cell. If the discharge sustaining voltage is applied across the corresponding scan electrode S and common electrode c, sustaining discharge occurs by electric particles produced at the time of address discharging between address electrode A and scan electrode S so that the light emission of cells is maintained for a given period of time.
An electric field is generated within the corresponding cell by discharge between the electrodes to accelerate a small amount of electrons among the discharge gas, and the accelerated electrons are collided with neutral particles of the gas to be ionized to electrons and ions. The ionized electrons are collided with neutral particles again, so the neutral particles are ionized to electrons and ions at high speed, thus producing vacuum ultraviolet rays, simultaneously with converting the discharge gas into a plasma. The produced ultraviolet rays exitate fluorescent layers 4 to generate visible rays, and as the visible rays are jetted out through upper substrate 1, the light emission of the corresponding cell can be recognized from the outside.
The discharge capacitance of ITO electrode 7 to which the discharge voltage is applied exerts a great influence upon the discharge. Referring to FIG. 3a, a distance between the electrodes is decreased by ITO electrodes 7 to lower the discharge voltage. However, this structure may increase the capacitance.
FIG. 3b depicts another conventional structure of discharge sustaining electrode with BUS electrode 8xe2x80x2 only without using the ITO electrode, and in this case, a distance dxe2x80x2 between the electrodes is increased to lower the capacitance, which makes the discharge voltage high to produce a discharge. In addition, if distance dxe2x80x2 between the electrodes is decreased, the switching rate may be lowered by BUS electrodes 8xe2x80x2.
Accordingly, the present invention is directed to discharge electrodes for a color plasma display panel (PDP) that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide discharge electrodes for a color plasma display panel which is capable of lowering a discharge voltage with an increased distance between discharge sustaining electrodes, thus lowering the power consumption of a PDP and enhancing the discharge efficiency.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the present invention discloses discharge electrodes for a color plasma display panel forming a discharge pair on one of two substrates coupled to each other spaced a given distance away from one another, including a transparent electrode positioned in the middle of a discharging cell; and opaque electrodes each spaced a given distance away from both sides of the transparent electrode and insulated by a dielectric layer. The opaque electrodes are made of metal. The transparent electrode is formed in parallel to the opaque electrodes. An external power supply is not applied to the transparent electrode. The transparent electrode is positioned with a different height from that of the respective opaque electrodes in the dielectric layer. The transparent electrode is positioned nearer a discharging space than the opaque electrodes.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.